1. Field of Invention
The present invention relates to a fan and a rotor thereof, and more particularly to a fan and a rotor thereof with high precision.
2. Related Art
Motors are widely used in various applications, such as a lathe, an electric drill and an electric saw in the industry, and a tape recorder, an optical drive, a hard disk drive, a pump, a blower, a dust cleaner, a refrigerator, a compressor of an air conditioner, and a fan in the daily life.
The fans are also widely used in dissipating heat generated from all electronic apparatuses, either the large industrial machines or the electronic products of the daily life, such as a power supply of a computer and an air conditioner.
As shown in FIG. 1, a conventional rotor 10 includes an impeller 11, an iron casing 12, a shaft 13 and a copper bushing 14. The impeller 11 is composed of a hub 111 and a plurality of blades 112. The copper bushing 14 is disposed at one end of the shaft 13. Conventionally, the copper bushing 14 is riveted to the iron casing 12, and then the protrusions 113 on the bottom of the hub 111 are respectively positioned in the openings 121 of the iron casing 12 correspondingly. The impeller 11 is connected to the iron casing 12 by way of hot melting or ultrasonic bonding. Thus, a complete rotor 10 is assembled.
However, the conventional rotor 10 has the following drawbacks.
First, when the impeller 11 is connected to the iron casing 12 by way of hot melting, the temperature rises so that the perpendicularity or the concentricity of the shaft 13 tends to be damaged due to different coefficients of thermal expansion of several different elements.
Second, when the impeller 11 is connected to the iron casing 12 by way of ultrasonic bonding, the perpendicularity or the concentricity of the shaft 13 tends to be damaged due to vibration caused by the ultrasonic bonding procedure.
Third, because of the multiple assemblies, in which the protrusion 113 on the bottom of the hub 111 has to be aligned with the opening 121 on the iron casing 12, another tolerance in addition to the original tolerance of the position of the opening 121 on the iron casing 12 is obtained due to the alignment and the bonding between the impeller 11 and the iron casing 12.
The damage to the perpendicularity or the concentricity of the shaft 13 and the accumulated tolerance tend to reduce production yield of the rotor 10, or even cause the skew and wear of the shaft 13. When the motor is rotating at the high speed, the problems caused by the skew and the wear tend to become more serious. It is thus imperative to provide a rotor structure, in which the perpendicularity or the concentricity of the shaft 13 is free from being influenced.